Thermally expandable material useful for reducing vibratioin transfer

ABSTRACT

A thermally expandable material is provided that, once expanded, has a Young&#39;s storage modulus E′ between 0.1 MPa and 1000 MPa, a loss factor of at least 0.3 (preferably, at least 1) and preferably a shear storage modulus G′ between 0.1 MPa and 500 MPa at a temperature between −10 and +40 degrees C. in the frequency range 0 to 500 Hz. Such materials are useful in combination with a carrier to form a dissipative vibratory wave barrier that effectively reduces the transfer of vibrations from a vibration generator, as may be present in a vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/542,928,filed 2 Oct. 2006, now allowed, which claims priority under the ParisConvention to European Patent Application No. 05292082.4, filed 6 Oct.2005, and incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to reducing the transfer of vibrationsgenerated by a vibration generator.

DISCUSSION OF THE RELATED ART

In a vehicle, the transfer of vibrations generated by a dynamic forcegenerator, such as an engine, a motor, a pump or a gear box, viastructural elements to an emitting surface such as a panel, leads to theemission of structure borne noise.

Different solutions have been suggested in order to at least reduce suchstructure borne noise. In vehicle construction, passive measures such asthe recourse to vibration dampers or dampening mats have been proposed.Such dampening mats are often applied on vibrating panels, e.g., in thedoors or on the floor of a vehicle. The extent of noise reduction ofthese methods is often unsatisfactory.

In the conventional process, mixtures of bitumen or asphalt and fillerswith a high specific weight are extruded into sheets, from which theappropriate shapes are punched or cut. These sheets are then bonded tothe appropriate metal sheet parts and must sometimes also be adapted tothe shape of the sheet by heating. Although these bitumen sheets arestill frequently used because of their low material cost, they are verybrittle and tend to peel off from the metal sheet, particularly at lowtemperatures. Also, the incorporation of additives which has often beenproposed only results in a slight improvement which is not sufficientfor many applications. Moreover, it is completely impossible to applythe pre-formed bitumen parts to the complex-shaped or almostinaccessible metal sheet parts of machines or vehicles, e.g., the innersurfaces of the cavities of motor vehicle doors. In addition, there isthe further disadvantage that in many cases several punched parts arerequired for only one vehicle or appliance and therefore costly storageis required.

There has consequently been no lack of attempts to eliminate thedisadvantages of bitumen sheets using other polymer systems. Forexample, aqueous polymer dispersions of polyvinylacetate orethylene-vinylacetate copolymers containing fillers were developed whichcan be sprayed on to the metal sheet parts with the necessary coatingthickness. These systems are, however, disadvantageous for industrialuse when there are high rates of production because the water cannot beremoved rapidly enough from the coating that is sprayed on, particularlywhen this coating is fairly thick.

The sound damping properties of polymer coatings are best in the rangeof the glass transition temperature of the polymer system, because dueto the viscoelasticity of the polymer in this temperature range themechanical energy of the vibration process is converted into heat bymolecular flow phenomena. Conventional sprayable coating materials basedon PVC plastisols, which, e.g., are widely used as an underbody coatingin motor vehicle construction, have no notable sound damping effect inthe application temperature range of −20 to +60° C. because the maximumvalue of the glass transition is about −20° C. to −50° C., depending onthe proportion of plasticizer.

Attempts were therefore made to modify these conventional PVC plastisolsso that they would have better sound damping properties in theapplication temperature range of −20° C. to +60° C. Coatings are knownfrom German published patent application 3514753 which contain multiplyunsaturated compounds, e.g., di- or triacrylates, peroxide cross-linkingagents and inorganic fillers, in conventional PVC plastisols. In thehardened state these plastisols are, however, glass-hard and brittle,and are therefore not really suitable for use in automobile constructionbecause they do not have sufficient flexibility, particularly at lowtemperatures. Apart from this, these formulations have a very low lossfactor tan δ and thus the sound damping effect is not very marked.

Compositions are described in German published patent application3444863 which contain PVC or vinylchloride/vinylacetate copolymers,optionally methylmethacrylate homopolymers or copolymers, a plasticizermixture and inert fillers. The plasticizer mixture comprisesplasticizers which are compatible with the methylmethacrylate polymersand plasticizers for the vinylchloride polymers which are incompatiblewith the methylmethacrylate polymers which may be present. Theplastisols thus obtained have improved sound damping properties comparedwith conventional PVC plastisols. However, particularly at temperaturesabove about 30° C., the sound damping effect drops again. If an attemptis made to shift the range of the maximum loss factor tan δ to highertemperatures by varying the relative quantities of the individualcomponents, the cold flexibility of the coating drops very severely. Areduced cold flexibility is, however, precisely what is disadvantageousin vehicle construction. In addition, the loss factor decreases veryseverely at lower temperatures with these formulations. These plastisolcompositions therefore have a sufficiently high loss factor only in avery narrow temperature range.

Furthermore, active measures for reducing structure borne noise havebeen developed. These measures usually employ sensors, signalprocessing, actuators, and power sources to counteract or effectivelyincrease the dissipation of the vibration by producing correspondingforces or strains.

Although active control measures have been shown to effectively reducestructure borne noise, they require sophisticated technical equipment,especially with respect to signal processing and sensors. This does notonly increase the costs, but also leads to an increased risk ofbreakdown.

Therefore, there is a need for an economic means for effectivelyreducing structure borne noise in a system, especially in a vehicle.

It is therefore an object of the present invention to overcome thedrawbacks of the prior art.

BRIEF SUMMARY OF THE INVENTION

After long and extensive research work the inventors have now found thateffective reduction of structure borne noise in a system such as avehicle may be achieved by way of a particular dissipative vibratorywave barrier, a particular thermally expandable material useful for themanufacture of said dissipative vibratory wave barrier, and a methodemploying said dissipative vibratory wave barrier.

The dissipative vibratory wave barrier according to the presentinvention comprises a carrier having an inner surface and an outersurface, the carrier having a polygonal section, especially rectangular,optionally U-shaped, and comprising on at least one of its outer surfaceor its inner surface a coating comprising a thermally expandablematerial selected among those which, after expansion and at atemperature between −10 and +40° C., have a Young's storage modulus E′between 0.1 MPa and 1000 MPa, preferably a loss modulus E″ between 0.5and 1, a loss factor greater than 0.3 (preferably, greater than 1) andpreferably also a shear storage modulus G′ between 0.1 MPa and 500 MPain the frequency range 0 to 500 Hz.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a first embodiment of adissipative vibratory wave barrier according to the present inventionbefore expansion of the thermally expandable material.

FIG. 2 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 1 after expansion of the thermally expandable material.

FIG. 3 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 1 after insertion into a structural element.

FIG. 4 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 3 after expansion of the thermally expandable material.

FIG. 5 is a graph showing three curves representing the variation of thestructure borne noise in a car body as a function of frequency.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

As previously mentioned, the thermally expandable material to be used incombination with a carrier is selected among those which, afterexpansion and at a temperature between −10 and +40° C., have a Young'sstorage modulus E′ between 0.1 MPa and 1000 MPa, preferably a lossmodulus E″ between 0.5 and 1, a loss factor greater than 0.3(preferably, greater than 1) and preferably also a shear storage modulusG′ between 0.1 MPa and 500 MPa in the frequency range 0 to 500 Hz.

Young's storage modulus (E′) is defined as the ratio of tensile stressto tensile strain below the proportional limit of a material. Shearstorage modulus G′ is defined as the ratio of shearing stress toshearing strain within the proportional limit and is considered ameasure of the equivalent energy stored elastically in a material. Theloss factor (also sometimes referred to as the structural intrinsicdamping or tan delta) is the ratio of the Young's loss modulus E″ overYoung's storage modulus E′ for the damping in tension compression. Forthe damping in shear, the loss factor is the ratio of the shear lossmodulus G″ over the shear storage modulus G′. These values may bereadily determined by Dynamic Mechanical Analysis (DMA) of a material,which in the context of this invention is the thermally expandablematerial after expansion. As is well known in the art, DynamicMechanical Analysis can be performed either by an indirect method wherethe material is characterized on a carrier (Oberst's beam test) or by adirect method where the tested sample is made only from the material tobe characterized (viscoanalyzer).

The carrier selected for use in the present invention has an innersurface and an outer surface. In cross-section, the carrier should bepolygonal in shape. Preferably, the cross-sectional shape of the carrierhas at least three sides that are straight lines and/or arcs. In oneembodiment, the carrier is open or partially open on one side, but inanother embodiment the cross-sectional shape of the carrier is closed.For example, the carrier in cross-section may have a shape selected fromthe group consisting of rectangular, square, pentagonal, hexagonal,U-shaped, and D-shaped. The sides of the carrier may be equal ordifferent in length, with the lengths of the sides generally beingselected in accordance with the interior dimensions of the structuralelement into which the dissipative vibratory wave barrier is to beinserted or the exterior dimensions of the structural element onto whichthe dissipative vibratory wave barrier is to be fixed. The carrier maybe completely hollow, but in certain embodiments could have one or moreinterior elements such as braces, ribs, cross-walls and the like. Thecarrier may be designed with small tabs, legs or other protrusions onits surface(s) or edge(s) that will face the bottom of the hollowstructural element into which the dissipative vibratory wave barrier isto be inserted. These protrusions are configured to hold such surface(s)or edge(s) away from the lower interior surface of the structuralelement, thereby allowing any of the liquids used in vehicle assemblyoperations to more completely coat or contact such lower interiorsurface. In the embodiment where the dissipative vibratory wave barrieris fixed onto the outside of the structural element, the surface of thebarrier having the coating of thermally expandable material positionedthereon and facing the exterior surface of the surface element may besimilarly held a relatively short distance away from such exteriorsurface by any suitable positioning means such as spacer elements,clips, flanges and the like.

In one embodiment of the invention, the carrier is straight. In otherembodiments, however, the carrier may be bent or curved. In still otherembodiments, the carrier may be straight in certain sections and curvedin other sections. Each side of the carrier may be planar (flat), but itis also possible for a side of the carrier to be non-planar (e.g.,curved or containing one or more indented areas and/or one or moreprotruding sections). The carrier sides may be continuous (free of anyopenings), but in certain embodiments one or more sides of the carriercould contain one or more openings. Generally speaking, the shape andconfiguration of the carrier are selected so as to generally parallel ormatch the contours or shape of the structural element into which thedissipative vibratory wave barrier is to be inserted or onto which thedissipative vibratory wave barrier is to be fixed and to clear anyelements within the structural element or on the exterior of thestructural element that might otherwise prevent the dissipativevibratory wave barrier, once coated with the thermally expandablematerial, from fitting within or onto such structural element. As willbe explained in more detail subsequently, it will be desirable to allowat least some clearance room between the outer surfaces of thedissipative vibratory wave barrier and the inner surfaces of thestructural element (in the embodiment where the barrier is to beinserted into the structural element) or between the inner surfaces ofthe dissipative vibratory wave barrier and the outer surfaces of thestructural element (in the embodiment where the barrier is to be fixedonto the outside of the structural element.

The carrier may be made of metal. Preferred metals are steel,particularly galvanized steel, and aluminum.

The carrier may also be made of a synthetic material, which mayoptionally be fiber reinforced (e.g., with glass fibers) and/orreinforced with other types of fillers. Preferred synthetic materialsare thermoplastic synthetic materials having a low water absorption anddimensionally stable up to at least 180° C. Suitable thermoplasticsynthetic materials may, for example, be selected within the groupconsisting of polyamides (PA), polyphenylene sulphides (PPS),polyphenylene ethers (PPE), polyphenylene sulfones (PPSU), polyetherimides (PEI) and polyphenylene imides (PPI). Thermoset syntheticmaterials such as molding compounds, rigid polyurethanes, and the likemay also be used to construct the carrier. The carrier may be formedinto the desired shape by any suitable method, such as, for example,molding (including injection molding), stamping, bending, extrusion andthe like.

Preferably, the carrier is relatively stiff. In one embodiment, thecarrier is at least as stiff at room temperature as the structuralelement into which the dissipative vibratory wave barrier will beinserted or onto which the dissipative vibratory wave barrier will befixed.

In the embodiment where the dissipative vibratory wave barrier is to beinserted into the structural element, the coating is applied to at leasta part of the outer surface of the carrier but may also be applied tothe whole outer surface. Similarly, in the embodiment where thedissipative vibratory wave barrier is to be fixed onto the structuralelement, the coating is applied to at least a part of the inner surfaceof the carrier but may also be applied to the whole inner surface. Thecoating of thermally expandable material may be continuous, although thepresent invention also contemplates having two or more separate portionsof the thermally expanded material on the outer or inner surface of thecarrier. These portions may differ in size, shape, thickness, etc.

The coating comprising the thermally expandable material may be uniformin thickness, but may also be varied in thickness over the outer orinner surface of the carrier. Typically, the coating will be from 0.5 to10 mm thick.

The thermally expandable material is a material that will foam andexpand upon heating but that is typically solid (and preferablydimensionally stable) at room temperature (e.g., 15-30 degrees C.). Insome embodiments, the expandable material will be dry and non-tacky, butin other embodiments will be tacky. The thermally expandable materialpreferably is formulated such that it is capable of being shaped ormolded (e.g., by injection molding or extrusion) into the desired formfor use, such shaping or molding being carried out at a temperatureabove room temperature that is sufficient to soften or melt theexpandable material so that it can be readily processed but below thetemperature at which expansion of the expandable material is induced.Cooling the shaped or molded expandable material to room temperatureyields a dimensionally stable solid having the desired shape or form.Upon activation of the blowing agent, i.e., upon being subjected to atemperature of between about 130° C. and 240° C. (depending on the exactformulation of expandable material that is used), the expandablematerial will typically expand to at least about 100% or at least about150% or alternatively at least about 200% of its original volume. Evenhigher expansion rates (e.g., at least about 1000%) may be selectedwhere required by the desired end use. When used in an automobile body,for example, the expandable material typically has an activationtemperature lower than the temperature at which primer or paint is bakedon the vehicle body during manufacture.

The thermally expandable material may be applied to the carrier surfaceby any suitable means such as extrusion, co-molding, over-molding, orthe like. For example, the thermally expandable material may be heatedto a temperature sufficient to soften or melt the material withoutactivating the blowing agent or curing agent that may be present and thesoftened or melted material then extruded as a ribbon onto the outer orinner carrier surface. Upon cooling, the ribbon of thermally expandablematerial then re-solidifies and adheres to the carrier surface.Alternatively, sheets of the thermally expandable material may be formedinto individual portions of the desired size and shape by die-cutting,with the individual portions then being attached to the outer or innersurface of the carrier by any suitable means such as mechanicalfasteners or heating the surface of the portion that is to be contactedwith the carrier surface to a temperature sufficient for the expandablematerial to function as a hot melt adhesive. A separately appliedadhesive layer may also be used to attach the thermally expandablematerial to the outer or inner surface of the carrier.

In an especially advantageous embodiment, the thermally expandablematerial comprises:

from 25 to 70% by weight, preferably from 35 to 55% by weight, of atleast one thermoplastic elastomer (preferably a styrene/butadiene orstyrene/isoprene block copolymer or at least partially hydrogenatedderivative thereof);

from 15 to 40% by weight, preferably from 20 to 35% by weight, of atleast one non-elastomeric thermoplastic (preferably an ethylene/vinylacetate or ethylene/methyl acrylate copolymer);

from 0.01 to 2% by weight, preferably from 0.05 to 1% by weight, of atleast one stabilizer or antioxidant;

from 2 to 15% by weight of at least one blowing agent, preferably anamount effective to cause the expandable material to expand at least100% in volume when heated at a temperature of 150 degrees C.;

from 0.5 to 4% by weight of one or more curing agents, optionallyincluding from 0.5 to 2% by weight of at least one olefinicallyunsaturated monomer or oligomer, and optionally;

up to 10% by weight (e.g., 0.1 to 10% by weight) of at least onetackifying resin;

up to 5% by weight (e.g., 0.1 to 5% by weight) of at least oneplasticizer;

up to 10% by weight (e.g., 0.1 to 10% by weight) of at least one wax;

up to 3% by weight (e.g., 0.05 to 3% by weight) of at least oneactivator for the blowing agent;

as well as optionally at least one filler (although the amount of filleris preferably less than 10% by weight, more preferably less than 5% byweight), the percentages being expressed as weight percentages of thetotal weight of the thermally expandable material.

Generally speaking, it will be desirable to use a thermoplasticelastomer that has a softening point no higher than the temperature atwhich the blowing agent begins to be activated, preferably at leastabout 30 degrees C. lower than the temperature that the expandablematerial will be exposed to when it is to be expanded. The thermoplasticelastomer is preferably selected within the group consisting ofthermoplastic polyurethanes (TPU) and block copolymers (including linearas well as radial block copolymers) of the A-B, A-B-A, A-(B-A)_(n-2)-B,A-(B-A)_(n-1) and (A-B)_(n)-Y types, wherein A is an aromatic polyvinyl(“hard”) block and the B block represents a rubber-like (“soft”) blockof polybutadiene, polyisoprene or the like, which may be partly orcompletely hydrogenated, Y is a polyfunctional compound and n is aninteger of at least 3. The blocks may be tapered or gradient incharacter or consist entirely of one type of polymerized monomer.

Hydrogenation of the B block removes originally present double bonds andincreases the thermal stability of the block copolymer. Such copolymersmay be preferred in certain embodiments of the present invention.

Suitable block copolymers include, but are not limited to, SBS(styrene/butadiene/styrene) copolymers, SIS (styrene/isoprene/styrene)copolymers, SEPS (styrene/ethylene/propylene/styrene) copolymers, SEEPS(styrene/ ethylene/ethylene/propylene/styrene) or SEBS(styrene/ethylene/butadiene/styrene) copolymers.

Especially suitable block copolymers include styrene/isoprene/styrenetriblock polymers, as well as fully or partially hydrogenatedderivatives thereof, in which the polyisoprene block contains arelatively high proportion of monomer moieties derived from isoprenehaving a 1,2 and/or 3,4 configuration. Preferably, at least about 50% ofthe polymerized isoprene monomer moieties have 1,2 and/or 3, 4configurations, with the remainder of the isoprene moieties having a 1,4 configuration. Such block copolymers are available from Kuraray Co.,Ltd. under the trademark HYBRAR and may also be prepared using themethods described in U.S. Pat. No. 4,987,194, incorporated herein byreference in its entirety.

In certain preferred embodiments of the invention the “hard” blocksrepresent from about 15 to about 30 percent by weight of the blockcopolymer and the “soft” blocks represent from about 70 to about 85percent by weight of the block copolymer. The glass transitiontemperature of the “soft” blocks is preferably from about −35 degrees C.to about 10 degrees C. while the glass transition temperature of the“hard” blocks is preferably from about 90 degrees C. to about 110degrees C. The melt flow index of the block copolymer preferably is fromabout 0.5 to about 6 (as measured by ASTM D1238, 190 degrees C., 2.16Kg). Typically, the block copolymer will have a number average molecularweight of from about 30,000 to about 300,000.

Examples of suitable thermoplastic polyurethanes (TPU) are those madeaccording to conventional processes by reacting diisocyanates withcompositions having at least two isocyanate reactive groups permolecule, preferably difunctional alcohols. Suitable organicdiisocyanates to be used include, for example, aliphatic,cycloaliphatic, araliphatic, heterocyclic and aromatic diisocyanates.

Specific examples of diisocyanates include aliphatic diisocyanates suchas, for example, hexamethylene-diisocyanate; cycloaliphaticdiisocyanates such as, for example, isophorone-diisocyanate,1,4-cyclohexane-diisocyanate, 1-methyl-2,4- and-2,6-cyclohexane-diisocyanate and the corresponding isomer mixtures,4,4′-, 2,4′- and 2,2′-dicyclohexylmethane-diisocyanate and thecorresponding isomer mixtures; and aromatic diisocyanates such as, forexample, 2,4-toluylene-diisocyanate, mixtures of 2,4- and2,6-toluylene-diisocyanate, 4,4′-diphenylmethane-diisocyanate,2,4′-diphenylmethane-diisocyanate and 2,2′-diphenylmethane-diisocyanate,mixtures of 2,4′-diphenylmethane-diisocyanate and4,4′-diphenylmethane-diisocyanate, urethane-modified liquid4,4′-diphenylmethane-diisocyanates and/or2,4′-diphenylmethane-diisocyanates,4,4′-diisocyanato-1,2-diphenyl-ethane and 1,5-naphthylene-diisocyanate.Diphenylmethane-diisocyanate isomer mixtures with a4,4′-diphenylmethane-diisocyanate content of greater than 96 wt. % arepreferably used, and 4,4′-diphenylmethane-diisocyanate and1,5-naphthylene-diisocyanate are used in particular. The diisocyanatesmentioned above can be used individually or in the form of mixtures withone another.

The compounds reactive with the isocyanate groups include, but are notlimited to, polyhydroxy compounds such as polyester polyols, polyetherpolyols or polycarbonate-polyols or polyols which may contain nitrogen,phosphorus, sulfur and/or silicon atoms, or mixtures of these. Linearhydroxyl-terminated polyols having on average from about 1.8 to about3.0 Zerewitinoff-active hydrogen atoms per molecule, preferably fromabout 1.8 to about 2.2 Zerewitinoff-active hydrogen atoms per molecule,and having a number average molecular weight of 400 to 20,000 g/mol arepreferably employed as polyol. These linear polyols often contain smallamounts of non-linear compounds as a result of their production. Thus,these are also often referred to as “substantially linear polyols”.

The polyhydroxy compounds with two or three hydroxyl groups per moleculein the number average molecular weight range of 400 to 20,000,preferably in the range of 1000 to 6000, which are liquid at roomtemperature, glassy solid/amorphous or crystalline, are preferablysuitable as polyols. Examples are di- and/or trifunctional polypropyleneglycols; random and/or block copolymers of ethylene oxide and propyleneoxide can also be used. Another group of polyethers that can preferablybe used are the polytetramethylene glycols (poly(oxytetramethylene)glycol, poly-THF), which are produced, e.g., by the acid polymerizationof tetrahydrofuran, the number average molecular weight range of thesepolytetramethylene glycols typically lying between 600 and 6000,preferably in the range of 800 to 5000.

The liquid, glassy amorphous or crystalline polyesters that can beproduced by condensation of di- or tricarboxylic acids, such as, e.g.,adipic acid, sebacic acid, glutaric acid, azelaic acid, suberic acid,undecanedioic acid, dodecanedioic acid, 3,3-dimethylglutaric acid,terephthalic acid, isophthalic acid, hexahydrophthalic acid, dimerizedfatty acid or mixtures thereof with low molecular-weight diols ortriols, such as, e.g., ethylene glycol, propylene glycol, diethyleneglycol, triethylene glycol, dipropylene glycol, 1,4-butanediol,1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol,dimerized fatty alcohol, glycerin, trimethylolpropane or mixturesthereof, are also suitable as polyols.

Another group of polyols to be used for making the TPU's are polyestersbased on ε-caprolactone, also known as “polycaprolactones”.

However, polyester polyols of oleochemical origin can also be used.These polyester polyols can be produced, for example, by the completering opening of epoxidized triglycerides of an at least partiallyolefinically unsaturated, fatty acid-containing fat mixture with one ormore alcohols with 1 to 12 C atoms and subsequent partialtransesterification of the triglyceride derivatives to alkyl esterpolyols with 1 to 12 C atoms in the alkyl radical. Other suitablepolyols are polycarbonate polyols and dimerized diols (Henkel), as wellas castor oil and its derivatives. The hydroxyfunctional polybutadienes,as obtainable, for example, with the trade name “Poly-bd”, can be usedas polyols for making the TPU's to be used according to the invention.

Preferably, combinations of polyether polyols and glassy amorphous orcrystalline polyester polyols are used for making the TPU's.

Preferably, the polyols have an average functionality towards isocyanatefrom about 1.8 to 2.3, preferably 1.9 to 2.2, particularly about 2.0.

The thermoplastic polyurethanes may also be made by additionally usingchain extending compounds like low molecular weight polyols such asethylene glycol, propylene glycol or butadiene glycol or low molecularweight diamines such as 1,2-diaminoethylene, 1,3-diaminopropylene or1,4-diaminobutane or 1,6-diaminohexane.

In preferred embodiments, the soft domains of the thermoplasticpolyurethane are selected from the group consisting of poly(ethyleneadipate), poly(1,4-butene adipate), poly(ethylene 1,4-butene adipate),poly(hexamethylene 2,2-dimethylpropylene adipate), polycaprolactone,poly(diethylene glycol adipate), poly(1,6-hexanediol carbonate) andpoly(oxytetramethylene).

Other thermoplastic elastomers suitable for use in the present inventioninclude other types of block copolymers containing both hard segmentsand soft segments such as, for example, polystyrene/polydimethylsiloxaneblock copolymers, polysulfone/polydimethylsiloxane block copolymers,polyester/polyether block copolymers (e.g., copolyesters such as thosesynthesized from dimethyl terephthalate, poly(tetramethylene ether)glycol, and tetramethylene glycol), polycarbonate/polydimethylsiloxaneblock copolymers, polycarbonate/polyether block copolymers,copolyetheramides, copolyetheresteramides and the like. Thermoplasticelastomers which are not block copolymers but which generally are finelyinterdispersed multiphase systems or alloys may also be used, includingblends of polypropylene with ethylene-propylene rubbers (EPR) orethylene-propylene-diene monomer (EPDM) rubbers (such blends often beinggrafted or cross-linked).

In addition to one or more thermoplastic elastomers, it is alsopreferred for the expandable material to contain one or morenon-elastomeric thermoplastics. Preferably, the non-elastomericthermoplastic is selected so as to improve the adhesion properties andprocessability of the expandable material. Generally speaking, it willbe desirable to use a non-elastomeric thermoplastic that has a softeningpoint no higher than the temperature at which the blowing agent beginsto be activated, preferably at least about 30 degrees C. lower than thetemperature that the expandable material will be exposed to when suchmaterial is to be expanded. Particularly preferred non-elastomericthermoplastics include olefin polymers, especially copolymers of olefins(e.g., ethylene) with non-olefinic monomers (e.g., vinyl esters such asvinyl acetate and vinyl propionate, (meth)acrylate esters such as C1 toC6 alkyl esters of acrylic acid and methacrylic acid). Exemplarynon-elastomeric thermoplastics especially suitable for use in thepresent invention include ethylene/vinyl acetate copolymers(particularly copolymers containing from about 20 to about 35 weight %vinyl acetate) and ethylene/methyl acrylate copolymers (particularlycopolymers containing from about 15 to about 35 weight % methyl acrylateand/or having Vicat softening points less than 50 degrees C. and/ormelting points within the range of 60 to 80 degrees C. and/or melt flowindices of from 3 to 25 g/10 minutes, as measured by ASTM D1238, 190degrees C., 2.16 Kg).

In certain embodiments of the invention, the weight ratio ofthermoplastic elastomer: non-elastomeric thermoplastic is at least 0.5:1or at least 1:1 and/or not greater than 5:1 or 2.5:1.

The tackifying resin may be selected within the group consisting ofrosin resins, terpene resins, terpene phenolic resins, hydrocarbonresins derived from cracked petroleum distillates, aromatic tackifyingresins, tall oil resins, ketone resins and aldehyde resins.

Suitable rosin resins are abietic acid, levopimaric acid, neoabieticacid, dextropimaric acid, palustric acid, alkyl esters of theaforementioned rosin acids, and hydrogenation products of rosin acidderivatives.

Examples of suitable plasticizers include C₁₋₁₀ alkyl esters of dibasicacids (e.g., phthalate esters), diaryl ethers, benzoates of polyalkyleneglycols, organic phosphates, and alkylsulfonic acid esters of phenol orcresol.

Suitable waxes include paraffinic waxes having melting ranges from 45 to70° C., microcrystalline waxes with melting ranges from 60 to 95° C.,synthetic Fischer-Tropsch waxes with melting points between 100 and 115°C. as well as polyethylene waxes with melting points between 85 and140°0 C.

Suitable antioxidants and stabilizers include sterically hinderedphenols and/or thioethers, sterically hindered aromatic amines and thelike.

All known blowing agents, such as “chemical blowing agents” whichliberate gases by decomposition or “physical blowing agents”, i.e.,expanding hollow beads (also sometimes referred to as expandablemicrospheres), are suitable as blowing agent in the present invention.Mixtures of different blowing agents may be used to advantage; forexample, a blowing agent having a relatively low activation temperaturemay be used in combination with a blowing agent having a relatively highactivation temperature.

Examples of “chemical blowing agents” include azo, hydrazide, nitrosoand carbazide compounds such as azobisisobutyronitrile,azodicarbonamide, di-nitroso-pentamethylenetetramine,4,4′-oxybis(benzenesulfonic acid hydrazide),diphenyl-sulfone-3,3′-disulfohydrazide, benzene-1,3-disulfohydrazide andp-toluenesulfonyl semicarbazide.

“Chemical blowing agents” may benefit from the incorporation ofadditional activators such as zinc compounds (e.g., zinc oxide),(modified) ureas and the like.

However, “physical blowing agents” and particularly expandable hollowmicrobeads are also useable. Advantageously, the hollow microbeads arebased on polyvinylidene chloride copolymers oracrylonitrile/(meth)acrylate copolymers and contain encapsulatedvolatile substances such as light hydrocarbons or halogenatedhydrocarbons.

Suitable expandable hollow microbeads are commercially available, e.g.,under the trademarks “Dualite” and “Expancel” respectively, from Pierce& Stevens (now part of Henkel Corporation) or Akzo Nobel, respectively.

Suitable curing agents include substances capable of inducing freeradical reactions, in particular organic peroxides including ketoneperoxides, diacyl peroxides, peresters, perketals, hydroperoxides andothers such as cumene hydroperoxide, bis(tert-butylperoxy)diisopropylbenzene, di(-2-tert-butyl peroxyisopropyl benzene),1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide,t-butylperoxybenzoate, di-alkyl peroxydicarbonates, di-peroxyketals(such as 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane), ketoneperoxides (e.g., methylethylketone peroxide), and4,4-di-tert-butylperoxy n-butyl valerate. The curing agent is preferablya latent curing agent, that is, a curing agent that is essentially inertor non-reactive at room temperature but is activated by heating to anelevated temperature (for example, a temperature within the range offrom about 130 degrees C. to about 240 degrees C.).

In a particularly desirable embodiment, the thermally expandablecomposition contains a small amount (e.g., 0.1 to 5 weight percent or0.5 to 2 weight percent) of one or more olefinically unsaturatedmonomers and/or oligomers such as C₁ to C₆ alkyl (meth)acrylates (e.g.,methyl acrylate), unsaturated carboxylic acids such as (meth)acrylicacid, unsaturated anhydrides such as maleic anhydride, (meth)acrylatesof polyols and alkoxylated polyols such as glycerol triacrylate,ethylene glycol diacrylate, triethylene glycol diacrylate,trimethylolpropane triacrylate (TMPTA) and the like, triallyl trimesate,triallyl trimellitate (TATM), tetraallyl pyromellitate, the diallylester of 1,1,3,-trimethyl-5-carboxy-3-(4-carboxyphenyl)indene,dihydrodicyclo pentadienyl acrylate, trimethylolpropane trimellitate(TMPTM), pentaerythritol trimethacrylate, phenylene-dimaleimide,tri(2-acryloxyethyl)isocyanurate, triallyl isocyanurate (TAIC), triallylcyanurate (TAC), tri(2-methacryloxyethyl)trimellitate, unsaturatednitriles such as (meth)acrylonitrile, vinyl compounds (including vinylaromatic compounds such as styrene), allyl compounds and the like andcombinations thereof. In one embodiment, the olefinically unsaturatedmonomer(s) and/or oligomer(s) used contain only one carbon-carbon doublebond per molecule (i.e., the monomer or oligomer is monofunctional withrespect to olefinically unsaturated functional groups). Preferably, themonomer(s) and/or oligomer(s) are selected to be capable of undergoingfree radical reaction (e.g., oligomerization or polymerization)initiated by the curing agent(s) present in the expandable material whenthe expandable material is heated to a temperature effective to activatethe curing agent (for example, by thermal decomposition of a peroxide).Examples of suitable fillers include ground and precipitated chalks,talc, calcium carbonate, carbon black, calcium-magnesium carbonates,barite and silicate fillers of the aluminium-magnesium-calcium type,such as wollastonite and chlorite. Preferably, however, the total amountof filler is limited to less than 10% by weight, more preferably lessthan 5% by weight. In one embodiment, the expandable material containsno filler (defined herein as substantially inorganic particles, such asparticles of the materials mentioned above).

In certain embodiments of the invention, the components of the thermallyexpandable material are selected such that the expandable material isfree or substantially free of any thermosettable resin such as an epoxyresin (e.g., the expandable material contains less than 5% or less than1% by weight epoxy resin).

Expansion of the thermally expandable material is achieved by a heatingstep, wherein the thermally expandable material is heated for a time andat a temperature effective to activate the blowing agent and also anycuring agent that may be present.

Depending on the nature of the thermally expandable material and theline conditions at the assembly line, the heating step is typicallycarried out at a temperature from 130° C. to 240° C., preferably from150° C. to 200° C., with a residence time in the oven from about 10 min.to about 30 min.

It is advantageous to take benefit of the heating step that follows thepassage of the vehicle parts in the generally used electro coating bath(E-coat bath) to cause expansion of the thermally expandable material asthe temperature during this heating step is generally sufficient tocause the expected expansion.

The present invention also relates to a method for reducing the transferof vibrations from a vibration generator to a location to which thevibration generator is connected via a structural element, comprisingequipping said structural element with means for dissipating vibrationalenergy generated by the vibration generator, characterized in that themeans for dissipating vibrational energy comprises a dissipativevibratory wave barrier according to the present invention as describedhere above.

Examples of vibration generators include motors, engines, pumps, gearboxes, suspension dampers and springs.

The method according to the present invention is particularly adaptedfor reducing structure borne noise in an automobile vehicle. In thiscase the vibration generator is connected to at least one of theconstitutive parts of the passenger compartment of said vehicle via astructural element. The shape of the structural element is that of atubular rail with a polygonal, preferably rectangular, cross-section.

The method according to the present invention comprises successively:

selecting a dissipative vibratory wave barrier according to the presentinvention having dimensions such that it can be inserted into thestructural element or fixed onto the structural element;

inserting the dissipative vibratory wave barrier into the structuralelement or fixing the dissipative vibratory wave barrier onto thestructural element in a location close to the vibration generator; and

expanding the thermally expandable material.

Advantageously, the dissipative vibratory wave barrier is selected suchthat a clearance of about 1 to 10 mm between the outer surfaces of thedissipative vibratory wave barrier and the inner surfaces of thestructural element (in the embodiment where the barrier is inserted intothe structural element) or between the inner surface(s) of thedissipative vibratory wave barrier and the outer surface(s) of thestructural element (in the embodiment where the barrier is fixed ontothe outside of the structural element) is obtained. Such an arrangementis desirable as it allows liquids such as cleaning baths, conversioncoating baths and electro coating (e-coat) baths to freely contact theinner and outer surfaces of the structural element. The inner and outersurfaces thus can be easily treated with such liquids after introductionof the dissipative vibratory wave barrier and prior to expansion of thecoating of thermally expandable material.

In another advantageous embodiment the cross-section of the dissipativevibratory wave barrier has the same shape as the cross-section of thestructural element. For example, if the structural element has arectangular cross-section with an interior length l and an interiorwidth w, the exterior dimensions of the dissipative vibratory wavebarrier (where the barrier is to be inserted into the structuralelement) will be l and w minus two times the clearance necessary for theexpanding material. The longitudinal length of the dissipative vibratorywave barrier generally should be selected so that it is no longer thanthe length of the structural element into which the wave barrier is tobe inserted or onto which the wave barrier is to be fixed. Typically,the dissipative vibratory wave barrier has a longitudinal length that isat least as long as the longest cross-sectional dimension of thecarrier, e.g., at least two or at least three times the length of thelongest cross-sectional dimension of the carrier. Longer lengths willpermit a greater quantity of the thermally expandable material to beintroduced between the structural element and the carrier, but generallyfor cost and weight reasons the quantity of such material used ispreferably not significantly in excess of the amount needed to achievethe desired extent of vibration transfer reduction.

The dissipative vibratory wave barrier is preferably inserted into thestructural element or fixed onto the structural element as close aspossible to the vibration generator and before the receiving vibratingstructure from which the sound is generated. If desired, any suitablemethod may be used to physically attach the dissipative vibratory wavebarrier to the structural element prior to activation of the thermallyexpandable material so that the barrier is secured in the desiredposition relative to the structural element, thereby preventingdisplacement of the barrier while the structural element is beingsubjected to further handling (as may be encountered in a vehicleassembly operation, for example). Such attachment may be accomplished,for example, through the use of mechanical fasteners such as clips,pins, screws, bolts, clamps and the like as well as through the use offlanges or tabs on one or both of the carrier and the structural elementthat are welded, riveted or adhesively attached so as to interconnectthe carrier and the structural element. The dissipative vibratory wavebarrier and the structural element may alternatively be configured in acooperative manner so that gravitational and/or frictional forces aloneare relied on to keep the barrier in place. For example, a U-shapeddissipative vibratory wave barrier that is to be fixed to the outside ofa rectangular shaped structural element may be designed to have flangesextending inward on each side of the open end of the U-shaped carrier.When the dissipative vibratory wave barrier is fitted around thestructural element, these flanges rest on the upper outer surface of thestructural element, thereby allowing the barrier to hang from thestructural element.

Expansion of the expandable material is obtained by a heating step.

Depending on the nature of the thermally expandable material and theline conditions at the assembly line, the heating step is typicallycarried out at a temperature from 130° C. to 240° C., preferably from150° C. to 200° C. with a residence time in the oven from about 10 min.to about 30 min.

To cause expansion of the thermally expandable material, it isadvantageous to take benefit of the heating step that follows the stepof passing the vehicle parts containing the dissipative vibratory wavebarrier through the generally used electro coating bath (E-coat bath),as the temperature during this heating step is generally sufficient tocause the desired expansion.

The amount of thermally expandable material that is applied to thecarrier is selected such that, after expansion, its volume occupies theclearance between the carrier and the surface of the structural elementthat faces the carrier. The thermally expandable material may beformulated such that it adheres to the inner or outer surface of thestructural element after expansion.

The hereindescribed dissipative vibratory wave barriers of the presentinvention can be used in any location within an automotive vehicleframe. For instance, such locations include, but are not limited to,pillars (including A, B, C and D pillars), rails, pillar to doorregions, roof to pillar regions, mid-pillar regions, roof rails,windshield or other window frames, deck lids, hatches, removable top toroof locations, other vehicle beltline locations, motor (engine) rails,lower sills, rocker panel rails, support beams, cross members, lowerrails, and the like.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description ofpreferred embodiments, reference being made to the accompanying figures,in which:

FIG. 1 is a schematic perspective view of a first embodiment of adissipative vibratory wave barrier according to the present inventionbefore expansion of the thermally expandable material;

FIG. 2 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 1 after expansion of the thermally expandable material;

FIG. 3 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 1 after insertion into a structural element;

FIG. 4 is a schematic perspective view of the dissipative vibratory wavebarrier of FIG. 3 after expansion of the thermally expandable material;and

FIG. 5 is a graph showing three curves representing the variation of thestructure borne noise in a car body as a function of frequency.

The dissipative vibratory ave barrier (1) shown in FIG. 1 comprises aU-shaped carrier (2) having an inner surface (2 a) and an outer surface(2 b). A coating (3) comprising a thermally expandable material isapplied to the outer surface (2 b). The initial thickness of theexpandable material may be, for example, 0.5 to 10 mm, e.g., 2 mm.

The U-shaped carrier (2) is made of metal or of a synthetic material.Preferred metals are galvanized steel and aluminium.

When using a synthetic material, these may optionally be fiberreinforced. The synthetic materials may be selected from thosepreviously recited. The thickness of the carrier (2) may be, forexample, 0.2 to 5 mm, e.g., approximately 1 mm. Preferably, thethickness of the metal or synthetic material is selected so as toprovide a carrier having a stiffness at least equal to the stiffness ofthe structural element to be combined with the dissipative vibratorywave barrier.

The following non-limiting example illustrates the invention and themanner of practicing the same.

As shown in FIG. 3, the dissipative vibratory wave barrier (1) isintroduced into a structural element of a car body, for example into afront member (4) having a longitudinal shape such as a rail or pillar.The structural element may already be enclosed when the dissipativevibratory wave barrier is introduced; for example, the structuralelement may be a hydroformed pillar or rail or a pillar or rail that hasbeen assembled by fastening together two or more sheet metal sections.Alternatively, the dissipative vibratory wave barrier may be introducedinto a channel-shaped section. After inserting the dissipative vibratorywave barrier (1), the channel-shaped section may be enclosed or sealedto form the structural element by placing a plate (which may be flat orformed into a nonplanar shape) on the open side of the channel-shapedsection, with the channel-shaped section and plate being preferablysecured to each other by suitable attachment means such as welding,adhesive bonding, mechanical fasteners, or some combination thereof.

As shown in FIG. 3, the dissipative vibratory wave barrier may have acarrier (2) that is approximately rectangular having the same exteriordimensions as the front member (4) minus the clearance necessary for theexpanding material (in this case minus 4 mm all around the carrier). Thedissipative vibratory wave barrier may be placed loosely (i.e., withoutphysical attachment) within the structural element or alternatively maybe fixed in position using one or more attachment devices such as clips,pins, bolts, screws, and the like. For example, the edges of the carrier(2) which come into contact with an inner surface of the structuralelement (4) may have one or more clips extending therefrom which areinserted into openings or other receptacles in said inner surface,thereby holding the dissipative vibratory wave barrier in place. Theclips may be configured such that the edges of the carrier (2) arepositioned a small distance away from the bottom of the structuralelement, thereby allowing cleaning compositions, conversion coatingcompositions, paint or primer compositions or any of the other liquidstypically used during vehicle assembly operations to more fully contactthe inner surface of the structural element.

After the insertion of the dissipative vibratory wave barrier (1), thecar body is heated to a temperature of 180° C. for 20 min in order tocause expansion of the thermally expandable material in the spacebetween the outer surface of the carrier (2 b) and the inner surface ofthe structural element. The activated dissipative vibratory wave barrieris illustrated in FIG. 4. After the heating, the coating of now-expandedexpandable material has a thickness of 4 mm. The expansion can berealized during the passage of the vehicle parts through an ovenfollowing treatment of the parts in an electro coating bath.

In other examples, the dissipative vibratory wave barrier (1) can beselected such that the clearance between the outer surfaces of thedissipative vibratory wave barrier (1) and the inner surfaces of thestructural element is about 1 to 10 mm. In all these cases, after theheating, the thermo-expandable material occupies all the clearance.

FIG. 5 shows the results of an experimentation carried out using a realcar body. In this experiment, the dissipative vibratory wave barrier islocated from the end of the front member and has a length of 52 cm.

A dynamic shaker is used as vibration generator and is attached at thefree end of the front longitudinal member in form of a rail of the carbody, with the dynamic shaker providing a wide band excitation in thefrequency range from 20 Hz up to 2000 Hz.

The injected vibration is measured by means of a force sensor located atthe entry point.

The response of the front floor and firewall panels to which thelongitudinal member is connected is measured by means of accelerometers.

The spaced averaged mobility of the floor panels is calculated (m/s/N)in the frequency range from 20 Hz up to 2000 Hz.

A comparison of the vibration levels is given in FIG. 5 while using theproposed invention onto the vibration transfer path and using classicaldamping mats applied directly on the vibrating panels. The curves showthe variation of the spaced averaged mobility as a function offrequency.

Three experiments are conducted:

without any added damping material on the vibrating panels and on thevibration transfer path (curve Cl on FIG. 5).

2.9 kg of conventional asphaltic damping mats are applied on thevibrating panels (front floor and firewall panels) (curve C2 on FIG. 5);this is the classical solution used on the studied car body to damp thevibration of the panels.

the dissipative vibratory wave barrier according to the invention asdescribed below is used (curve C3 on FIG. 5).

The expandable material had the following composition:

45 parts by weight SIS block copolymer, styrene content 20%

5 parts by weight aromatic hydrocarbon resin as tackifier

2.5 parts by weight diisononylphthalate

4.5 parts by weight microcrystalline wax

27.5 parts by weight thermoplastic ethylene/vinyl acetate copolymer (28%vinyl acetate)

0.1 parts by weight phenolic antioxidant

8.8 parts by weight blowing agent (azodicarbonamide)

1.0 parts by weight 1,1-di-tert-butylperoxi-3,3,5-trimethylcyclohexane

0.5 parts by weight methylacrylate

1.5 parts by weight zinc oxide treated urea.

From curves C1 and C2, it appears that in the frequency range ofstructure borne noise between 100 Hz and 500 Hz, the spaced averagedmobility is reduced by an average of 5.0 dB. Since the spaced averagedmobility is directly proportional to the structure borne noise, noisereduction is also 44%.

By comparison of curves C3 and C2, it appears that in the frequencyrange of structure borne noise between 100 Hz and 500 Hz the spacedaveraged mobility is reduced by an average of 1.4 dB, i.e. 15%.

The superiority of the solution proposed by the invention with respectto the most frequently used prior art solution (vibration dampers anddampening mats) clearly appears when comparing the reduction of noiseobtained due to the invention, i.e., 44% and the reduction obtained whenusing the prior art solution, i.e., 15%.

The principal advantages of the invention are as follows:

much less material is necessary to damp the vibration of the vibratingpanels;

the use of the dissipative vibratory wave barrier according to theinvention is much cheaper in term of process costs for the car ormachinery manufacturer compared to the application of damping materialto the vibrating panels;

the ability to work on transmission paths requires a more in-depthanalysis of the vehicle body structure but allows the solution to betuned on a given excitation source or frequency range compared to amulti-purpose solution as the treatment of the panels;

the use of the dissipative vibratory wave barrier according to theinvention may also contribute to the rigidity of the frame thusimproving the safety and comfort of the vehicle, however a substantialcontribution to the rigidity of the frame will always reduce theefficacy of the dissipative vibratory wave barrier property.

1. A thermally expandable material that when expanded has a Young'sstorage modulus E′ between 0.1 MPa and 1000 MPa and a loss factor higherthan 0.3 at a temperature between −10 and +40 degrees C. in thefrequency range 0 to 500 Hz.
 2. A thermally expandable material inaccordance with claim 1, wherein said thermally expandable materialcomprises at least one thermoplastic elastomer, at least onenon-elastomeric thermoplastic, at least one stabilizer or antioxidant,at least one blowing agent, and at least one curing agent.
 3. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material is comprised of at least one peroxidecuring agent.
 4. A thermally expandable material in accordance withclaim 1, wherein said thermally expandable material is comprised of atleast one thermoplastic elastomer selected from the group consisting ofthermoplastic polyurethanes, styrene/butadiene block copolymers,hydrogenated styrene/butadiene block copolymers, styrene/isoprene blockcopolymers, and hydrogenated styrene/isoprene block copolymers.
 5. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material is comprised of at least onenon-elastomeric thermoplastic selected from the group consisting ofethylene/vinyl acetate copolymers and ethylene/methyl acrylatecopolymers.
 6. A thermally expandable material in accordance with claim1, wherein said thermally expandable material is comprised of at leastone olefinically unsaturated monomer or oligomer.
 7. A thermallyexpandable material in accordance with claim 1, wherein said thermallyexpandable material is comprised of at least one plasticizer.
 8. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material is comprised of at least one wax.
 9. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material is comprised of at least one latentchemical blowing agent.
 10. A thermally expandable material inaccordance with claim 1, wherein said thermally expandable material iscomprised of at least one tackifying resin.
 11. A thermally expandablematerial in accordance with claim 1, wherein said thermally expandablematerial is comprised of at least one blowing agent activator.
 12. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material is comprised of at least onestyrene/isoprene/styrene triblock polymer or fully or partiallyhydrogenated derivative thereof with at least about 50% of thepolymerized isoprene monomer moieties having 1,2 and/or 3,4configurations.
 13. A thermally expandable material in accordance withclaim 1, wherein said thermally expandable material comprises: a). from25 to 70% by weight of at least one thermoplastic elastomer; b). from 15to 40% by weight of at least one non-elastomeric thermoplastic; c). from0.01 to 2% by weight of at least one stabilizer or antioxidant; d). from2 to 15% by weight of at least one blowing agent; and e). from 0.5 to 4%by weight of at least one curing agent.
 14. A thermally expandablematerial in accordance with claim 1, wherein said thermally expandablematerial comprises: a). from 35 to 55% by weight of at least onethermoplastic elastomer selected from the group consisting ofthermoplastic polyurethanes, styrene/butadiene block copolymers,hydrogenated styrene/butadiene block copolymers, styrene/isoprene blockcopolymers, and hydrogenated styrene/isoprene block copolymers; b). from20 to 35% by weight of at least one non-elastomeric thermoplasticselected from the group consisting of ethylene/vinyl acetate copolymersand ethylene/methyl acrylate copolymers; c). from 0.05 to 1% by weightof at least one stabilizer or antioxidant; d). at least one latentchemical blowing agent in an amount effective to cause the expandablematerial to expand at least 100% in volume when heated at a temperatureof 150 degrees C. for at least 20 minutes; e). from 0.5 to 4% by weightof at least one peroxide; and f). from 0.5 to 2% by weight of at leastone olefinically unsaturated monomer or oligomer; wherein said thermallyexpandable material contains less than 10% by weight filler.
 15. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material comprises: a). from 25 to 70% by weight ofat least one thermoplastic elastomer; b). from 15 to 40% by weight of atleast one non-elastomeric thermoplastic; c). from 0.01 to 2% by weightof at least one stabilizer or antioxidant; d). from 2 to 15% by weightof at least one blowing agent; e). from 0.5 to 4% by weight of at leastone curing agent; f). at least one tackifying resin, in an amount up to10% by weight; g). at least one wax, in an amount up to 10% by weight;and h). at least one plasticizer, in an amount up to 5% by weight.
 16. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material comprises: a). from 35 to 55% by weight ofat least one styrene/isoprene block copolymer thermoplastic elastomerselected from the group consisting of styrene/isoprene block copolymers;b). from 20 to 35% by weight of at least one non-elastomericthermoplastic selected from the group consisting of ethylene/vinylacetate copolymers; c). from 0.05 to 1% by weight of at least onestabilizer or antioxidant; d). at least one latent chemical blowingagent in an amount effective to cause the expandable material to expandat least 100% in volume when heated at a temperature of 150 degrees C.for at least 20 minutes; e). from 0.5 to 4% by weight of at least oneorganic peroxide; f). from 0.5 to 2% by weight of at least one C₁ to C₆alkyl (meth)acrylate; g). at least one tackifying resin, in an amount upto 10% by weight; h). at least one plasticizer, in an amount up to 5% byweight; and i). at least one wax, in an amount up to 10% by weight;wherein said thermally expandable material contains less than 10% byweight filler.
 17. A thermally expandable material in accordance withclaim 16, wherein at least about 50% of the polymerized isoprene monomermoieties in said at least one styrene/isoprene block copolymerthermoplastic elastomer have 1,2 and/or 3,4 configurations.
 18. Athermally expandable material in accordance with claim 1, wherein saidthermally expandable material comprises: a). from 35 to 55% by weight ofat least one styrene/isoprene block copolymer thermoplastic elastomerselected from the group consisting of styrene/isoprene block copolymers;b). from 20 to 35% by weight of at least one non-elastomericthermoplastic selected from the group consisting of ethylene/vinylacetate copolymers; c). from 0.05 to 1% by weight of at least onestabilizer or antioxidant; d). at least one latent chemical blowingagent in an amount effective to cause the expandable material to expandat least 100% in volume when heated at a temperature of 150 degrees C.for at least 20 minutes; e). from 0.5 to 4% by weight of at least onecuring agent capable of inducing free radical reactions; g). at leastone tackifying resin, in an amount up to 10% by weight; and h). at leastone plasticizer, in an amount up to 5% by weight.
 19. A thermallyexpandable material in accordance with claim 18, wherein at least about50% of the polymerized isoprene monomer moieties in said at least onestyrene/isoprene block copolymer thermoplastic elastomer have 1,2 and/or3,4 configurations.